Luminaire



July 31, 1962 J oxn: ETAL 3,047,716

LUMINAIRE Filed Jan. 31, 1961 INVENTORS JbH/v P flax/E AND ITIEANKLIN MNEAL United States Patent Office 3,047,716 Patented July 31, 19623,047,716 LUMINAIRE John P. Hoxie and Franklin M. Neal, Corning, N.Y.,assignors to Corning Glass Works, Corning, N.Y., a corporation of NewYork Filed Jan. 31, 1961, Ser. No. 86,208 2 Claims. (Cl. 2401.2)

The present invention relates to a luminaire which is adapted to berecessed substantially flush with a surface such as an airport runwayand which is capable of emitting light at low angles of elevation abovesuch surface.

It has generally been the practice to delineate airport runways at nightby means of two rows of lights located one at each edge of the runwayand projecting substantially thereabove. Recent conditions of increasedair traffic have indicated the advisability of placing lights in therunway surface itself in order to render the runway more easily visiblefrom the air.

In the construction of luminaires adapted for such use, it has been aproblem to design units capable of directing light at low angles ofelevation along an incoming flight path and at the same timesufficiently nearly flush with the runway surface so as to permitairplanes to taxi along the runway Without being subject to excessivevibration.

It has also been a problem to design a unit sufliciently compact topermit installation in presently existing runways with a minimum ofexcavation.

The luminaire of the present invention has among its objects thesatisfaction of the above requirements.

In general, these objects are accomplished by the provision of aluminaire comprising a lens with a light source on the approach side ofa lens, the lens including an entrance surface, a reflecting surface,and an exit surface, said luminaire being positioned so that the twofirst-mentioned surfaces are substantially beneath the level of therunway surface and the last-mentioned surface is only partially abovethe said level but completely exposed to view.

The construction of one embodiment of a luminaire according to thepresent invention may best be considered with reference to theaccompanying drawings, wherein:

FIG. 1 is a perspective view of a lens and light source according to thepresent invention,

FIG. 2 is a sectional view taken along line 22 of FIG. 1,

FIG. 3 is a top view of one form of a luminaire adapted for seating in acylindrical hold in a runway, and

FIG. 4 is a view taken through line 4-4 of FIG. 3.

The construction of the novel lens employed in the present luminaire isillustrated in FIGS. 1 and 2. Light from source 11 enters lens 12through entrance surface 13, is reflected from reflecting surface 14,which is a coating of silver or any other reflecting substance, andemerges from exit surface 15.

In the illustrated embodiments, entrance surface 13 and exit surface 15are plane surfaces, entrance surface 13 being vertical, and reflectingsurface 14 is curved in both horizontal and vertical directions suchthat, when the light source is considered to be a point, the cumulativeeffect of the three surfaces is to collimate the emergent rayshorizontally and to spread them vertically over angles of elevationabove the horizontal varying continuously from 8 for those rays emergingnear the bottom of exit surface 15 to 1 for those rays emerging near thetop of that surface. These angles are illustrated in FIG. 2 by theangles b and a respectively. In other embodiments curved and planesurfaces may be interchanged.

In the illustrated embodiment light source 11 is in the form of ahorizontal linear filament positioned parallel to entrance surface 13. Aconsequence of the finite horizontal length of the filament is thatlight emerging from the lens is spread over a few degrees in ahorizontal plane, the spread depending upon the length of the filamentand its distance from the lens. This small spread is desirable in orderto render the signal visible from positions slightly off the sides ofthe runway. Variations in filament size and distance may be offset byVariations in the horizontal curvature of reflecting surface 14.

The effect of lens 12 on the vertical orientation of light raysoriginating at the center of filament 11 can be seen in FIG. 2. Rays 20and 21 are refracted at entrance surface 13, are reflected from surface14 and emerge at angles of elevation of 1 and 8 respectively after beingrefracted at exit surface 15. The lens is adapted to bend raysintermediate between rays 20 and 21 through angles varying between 1 and8.

Lens 12 is recessed almost completely beneath the level of the surfaceof the runway. A convenient means for embedding the lens in a runway andat the same time insuring that most of the rays emitted from exitsurface 15 are utilized is provided by mounting unit 25, illustrated inFIGS. 3 and 4. This unit comprises a cylinder having a heightapproximately equal to that of lens 12 and a diameter suflicient topermit inclusion of the lens and light source 11 in a cavity in themounting unit. Lens 12 extends above the top surface of the mountingunit 25 only by an amount suflicient to present a substantial viewingsurface at low elevations above the runway surface, which issubstantially flush with the upper surface of the mounting unit when theunit is in position. It is unnecessary that all of exit surface 15extend above the runway surface level since, as indicated in FIG. 2,those rays which are directed at low angles of elevation are emittednear the top of the exit surface, while the lower portion of saidsurface directs light at higher angles, at which angles obstruction fromthe rim of mounting unit 25 or the surface of the runway is less of aproblem.

Light source 11 is positioned within the cavity of mounting unit 25 andon the approach side of lens 12, which side is the side from which alanding airplane approaches the luminaire. A transparent cover 26 maycomplete the enclosure of light source 11 and prevent the accumulationof deposits in the cavity.

It can be seen that only a small portion of the light emitted fromsource 11 is directed within the desired range. The efficiency of thedevice can be improved by placing a reflector behind the light source.It will also be observed that some light will enter the lens at anglesoutside the range between the angles of rays 20 and 21. These rays willemerge from the lens in various directions but the intensity in anygiven direction will be low.

It will be readily seen that the advantages of the present inventionwill accrue even though variations are made in the exact configurationof the luminaire. A cylindrical mounting unit has been chosen because ofthe ease with which circular holes may be formed in a runway. It isapparent that no arbitrary dimensions may be given to lens 12 and thatvarious combinations of shapes of entrance, reflecting and exit surfaceswithin the spirit of the present invention will produce the desiredpattern of emergent light.

The range of elevation of the emergent rays in the illustratedembodiment has been chosen to be between 1 and 8 since presentconditions of air traflic indicate this range to be optimum. Underchanged conditions, this range may be varied by changes in theconfiguration of lens 12 within the spirit of the invention. The exactconfiguration of lens 12 can easily be determined to satisfy varyingrequirements by those skilled in the art according to wellknownmathematical and optical laws.

Accordingly, it is intended that the present invention be limited onlyby the scope of the appended claims.

What is claimed is:

1. A luminaire for directing light through a range of low angles ofelevation above a horizontal surface comprising .a light source locatedbelow the level of said horizontal surface and a lens extending fromslightly above saidvhorizontal surface to a level silghtly below saidlight source, said lenscompr-ising an entrance surface located on thesame side of said lens as said light source positioned to receive lightrays therefrom, an exit surface located on the same side of said lens assaid light source and at the top oftsaid lens and forming an acute anglewith said horizontial surface when measured in the direction away fromsaid light source, and a reflecting surface located at the 1 side ofsaid lens opposite said light source, said reflecting surface beingcurved in both horizontal and vertical directions, said lens spreadinglight from said source vertically through angles of elevation above saidhorizontal surface varying continuously from a maximum for lightemerging near the bottom ofi said exit surface to a minimum for lightemerging near the top thereof.

2. A luminaire according to claim 1 wherein said refleeting surfacesubstantially collimates horizontally the 10 light from said lightsource falling thereupon.

References Cited in the file of this patent FOREIGN PATENTS

